A previously proposed quick connect coupling of this kind is disclosed in European Patent No. EP-A-0 532 242. Upon insertion of the first fluid conduit in the second fluid conduit, the sleeve embraces the first conduit and is inserted completely into an end section of the second conduit. The length of the end section is at least equal to the length of the sleeve. This ensures that the first conduit is sufficiently supported against lateral deflection in the second conduit. In addition, the coupling ring engages the inside of the second conduit. However, this design means that the second conduit must have an end section of suitable length and wall thickness. The end section is therefore costly in terms of material, particularly if the second conduit is a connecting piece which is formed on the receptacle wall, for example, the radiator of a motor vehicle.